1

Basic Symbols

2

Student Entity type using E-R notation

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Multivalued – Employee

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Weak (attributive) entity

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Example relationships of different degrees

10.510.5

6

Bill of Materials Unary Relationship

(a) Many-to-Many Relationship

(b) Two Instances

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CA

Consider the Is_married_to unary relationship 1. Assume we want to know the date on which a marriage

occurred. Augment this ER diagram to include a Date_married attribute.

2. Since sometimes persons remarry after the death of a spouse or divorce, redraw this ERD to show the whole history of marriages for person. Show the Date_married attribute on this diagram.

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1

PERSON

Is_Married_to

Date_Married

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2.

PERSON

Married Date_Married

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Optional cardinalities

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Mandatory Cardinalities

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One optional, one mandatory cardinality

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1:M Relationship(ERD)

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M:M Relationship(tbl)

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M:M Relationship(ERD)

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IS-A Relationships(tbl)

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IS-A Relationships (ERD)

19

CA

In a real state DB, there is an entity called PROPERTY, which is a property for sale by the agency. Each time a potential property buyer makes a purchase offer on a property, the agency records the date, offering price, and name of the person making the offer.a. Represent the PROPERTY entity and its purchase offer attributes

using the notation for multivalued attributes.

b. Represent the PROPERTY entity and its purchase offer attributes using two entity types.

c. Finally, assume the agency decides to also keep data about buyers and potential buyers, including their name, phone number, and address. Augment your answer to part b above to accommodate this new entity type.

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a.

PROPERTY

Offer_Date, Offer_Price Offer_Name

Property_No

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b.

OFFER

Property_No

PROPERTY

Offer_No

Offer_Date

Offer_Price

Offer_Name

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c.

OFFER

Property_No

PROPERTY

Offer_No

Offer_Date

Offer_Price

OFFER

Property_No

PROPERTY

Offer_No

Offer_Date

Offer_Price

POTENTIAL_ BUYER

Buyer_No

Phone_No Address

Name

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CA - Draw a ER diagram for the following

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PRODUCT

CUSTOMER

ORDER

Places

Includes

Name

Customer_No

Street_Address City

State

Zip

Order_No

Order_Date

Promise_Date

Quantity

Product_No

Description

Unit_Price

ERD – customer order